Color display devices

ABSTRACT

A display device for exhibiting a color pattern, said device comprising container means having a light-transmitting section and a juxtaposed darker hued or opaque section, a quantity of liquid crystalline material interposed between said container sections and encapsulated within said container means, said material having a characteristic of selective light scattering to exhibit color patterns within a range of temperatures at which said display device is normally utilized, and means for peripherally sealing one of said container sections to the other. Means can also be provided for applying deformational stress to the liquid crystal to vary its color pattern.

United States Patent Sharpless et al.

[ Mar. 7, 1972 [54] COLOR DISPLAY DEVICES [72] Inventors: Edward N.Shnrpless, Pitcairn; Frederick [2! 1 Appl. No.: 40,925

[52] US. Cl ..350/l60, 40/ I30, 356/32 [5 l] Int. Cl. ..G02t H40 [58]Field of Search ..356/32; 350/160; 40/130 [56] References Cited UNITEDSTATES PATENTS 3,441,513 4/ 1969 Woodmansee ..350/ 160 LC OTHERPUBLICATIONS Product Engineering, Dec. 21, 1964, Vol. 35, pp. 56 57.Ferguson, Liquid Crystals, Scientific American, Vol. 21], 8/64, pp. 76-85.

Wysooki et al., Molecular Crystals & Liq. Crystals, Vol. 8, 8/6 p 47 l-488.

Adams et al., Molecular Crystals & Liq. Crystals, Vol. 8, 8/68, pp. 9-l8.

Klein et 21]., Rev. of Sci. lnstr., Vol. 41, No. 2, 2/70, pp. 238 239.

Garn, J. of Amer. Chem. Soc., Vol. 91, No. 19, 9/69, p. 5382. Lehmann,Thermodynamics, Vol. I, 1966, pp. 2- 5.

Fergason et al., Electro- Technology, l/70, pp. 41- 50.

Primary Examiner-Ronald L. Wibert Assistant Examiner.l. RothenbergAttorney-Donn J. Smith [57 ABSTRACT A display device for exhibiting acolor pattern, said device comprising container means having alight-transmitting section and a juxtaposed darker hued or opaquesection, a quantity of liquid crystalline material interposed betweensaid container sections and encapsulated within said container means,said material having a characteristic of selective light scattering toexhibit color patterns within a range of temperatures at which saiddisplay device is normally utilized, and means for peripherally sealing'one of said container sections to the other. Means can also be providedfor applying deformational stress to the liquid crystal to vary itscolor pattern.

20 Claims, 54 Drawing Figures PATENTEUMAR 71912 3, 647, 279

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rang aw mavzn" COLOR DISPLAY DEVICES The present invention relates tovariable color display or aesthetic devices and to means for enhancingthe variable color patterns produced by the device for entertainment,advertising, aesthetic or decorative effects or purposes.

Devices for displaying color patterns for various purposes are legion.These devices usually employ various colored materials or surfaces,color filters or simply lights of various colors. Many of these devicesare capable only of displaying colors or color patterns of a fixed orinvarying nature, and their usefulness is thereby limited. Particularlyin displays for decorative or aesthetic purposes, the novelty wears off"all too soon.

Color display devices in the form of various kinds of lightprojectingmachines are likewise available for use in advertising, entertainmentand in the purely decorative field. For the most part, these machinesrely on solid crystalline or plastic colored materials, photographicslides, systems of mirrors with color filters attached, movable arraysof color filters, or simply lights of various colors which may bemovably disposed or otherwise sequenced to illuminate the object or areawith the intended color pattern or patterns. While some of thesemachines work reasonably well in a limited range of applications andfurnish a number of fixed color patterns, the machines usually arecomplex in construction owing to mechanical repetition of variouscomponents. The total number of available color patterns or colorvariation is severely limited in most cases and the sense of variety issoon lost. The colors or color patterns are usually overly brilliant,cold, or otherwise unnatural in their hues and intensities.

In many color display devices there is the frequent requirement thatseveral such devices or systems be used to approach the desiredaesthetic or decorative effects. The number of moving components ofthese systems are thereby multiplied, leading to maintenance problems.When several. such light systems are utilized, a time synchronization isoften required, particularly when one attempts to associate music with achanging color display or an analogous dynamic lighting system. Thisobjective is difficult to accomplish with conventional systems owing tolarge numbers of moving parts and other practical difficulties.Moreover, the potential variation in color patterns has been severelylimited for the reasons pointed out above.

In many other fields of endeavor, it is desired to illuminate relativelylarge areas in varying color patterns. For example, in the fields oftheatrical and nightclub lighting, various means have been utilized forproviding colored illuminational patterns, for backdrop or otherenvironmental effects. Frequently, a subdued character is desired ofthese environmental effects. This is accomplished by rather complexlighting systems, as alluded to above, requiring, where moving patternsare desired, the services of a skilled operator to arrange the necessarycombination of lighting components, to achieve a desired sequence ofcolors or color patterns. Conventionally theatrical lighting systems forthis purpose include a light source with a plurality ofsolenoid-operated color filters for selective orientation in front ofthe light source for varying the color saturation with which the stageis illuminated. Such equipment may require several hundred color panels,and numerous light sources, all of which must be operated by skilledpersonnel. Other arrangements involve complicated arrays of mirrorsand/or projectors, none of which is capable of changing color patternswith smooth transitions between colors and hues.

Certain of these problems have been alleviated to some extent byprojection and display devices disclosed in the U5. Pats. to Clark, 111No. 3,431,044; Lane et al. No. 3,3l5,39l; and Billings No. 2,600,962.The Clark device inherently involves a number of moving parts butlimited color variation.

1 The potential color variations achieved by the Clark device A similararrangement is shown in the Lane et al. reference in which theintermediate solid member is additionally deformed to simulate motion.The Billings device is analogous, except that a stress-responsivebirefringent crystal is employed. The Billings arrangement, moreover, isnot directed to the problem of aesthetic or decorative lighting, as itis arranged to pass very narrow optical bands.

in general, the variety of color patterns attainable with devices suchas disclosed by Lane et al. and Clark is limited, owing to theemployment of birefringent solid members. The cited references requirethe use of various light polarizing structures, which are not essentialto our invention. Our color display device, which can be more or lesspermanently and directly applied to large surface areas, such as walls,ceilings, stage backdrop, and furniture surfaces, in many cases obviatesthe need for colored lights or the optical projection of color patterns.

We overcome these disadvantages of the prior art by providing a uniqueoptical display device capable of producing an infinite variety of colorvariations and patterns. The solution of this perennial problem isrealized by introducing a liquid crystalline material into a displaydevice of novel construction. Desirably the liquid crystalline materialis selected which has a characteristic of variable light scattering atroom temperature or at least at those environmental temperatures underwhich the device is employed. For example, a liquid crystalline materialcan be selected, which is capable of variable light scattering atoperating temperatures in the region of an illuminating light source,for example one utilized in an advertising sign, area lighting, or otherdisplay arrangement. The selected liquid crystalline material desirablybut not necessarily exhibits a variable scattering characteristic whichis further modified when subjected to mechanical deformation, such asoccasioned by shear or flow stresses.

Accordingly, our novel display device or liquid crystal cell is providedfirstly with a light transmitting wall to permit viewing of thecontained liquid crystalline material. Secondly, the liquid crystallinecell is desirably associated with means for inducing deformationalstresses within the contained liquid crystalline material. This can beaccomplished in a variety of ways: For examples, the liquid crystallinecell can be constructed with means permitting the displacement of onewall structure thereof relative to another. Various mechanical means canbe associated with the cell or display device for inducing flow andattendant shear stresses within the liquid crystalline material.

Our display device as thus far described is capable of a large number ofapplications, for example as an aesthetic novelty, decorative wall,floor and ceiling panels, backdrops for stages and other illuminatedareas, toys, book and album covers, place mats, paper weights, clockfaces, displays for table tops and other furniture surfaces, andnumerous analogous applications. For many of these applications asubdued background or environmental illumination is sufficient forviewing the infinite variety of color patterns resulting from a stressmanipulation of my display device. Deformational stresses can be appliedmanually or through the operation of suitable mechanical,electromechanical, or electrohydraulic means. Owing to the pressuresensitivity of many liquid crystalline materials, useful in ourinvention, stresses can be applied by vibratory or minor shock energies.For example, certain forms of the .display device can be suspended orstretched over loudspeaker, or the like, such that color pattern changesare effected by sonic vibrations. An analogous application involvesincorporation of my display device on piano tops or in connection withother musical instruments.

In many other applications, our liquid crystal display devices findutilization where it is desirable to show visually strain patterns, orpatterns of stress application. For example, components of our displaydevices can be applied to such items as glass or metal sheets todemonstrate physical stresses therein.

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minim Conventionally, the usefulness of cholesteric liquid crystaltinematerials has been severely limited owing to their ,greaselike nature.There has been no adequate conventional means for protecting the liquidcrystalline material from a hostile environment such as dirt, dust, oiland accidental removal of the material from the surface to which it isapplied. Various means for encapsulating liquid crystals have beenproposed from time to time. According to one such attempt, the liquidcrystalline material is encapsulated as minute balls or droplets in agelatin matrix. The form of encapsulation, however, does not permit thevisual stress phenomenon to be observed and greatly diminishes thelight-scattering characteristic of the liquid crystal. Other attempts,involving a simple overlay with a protective material, have met withfailure in the absence of an adequate sealing means for excludingelements of a hostile environment.

With the application of deformational stresses to the liquid crystallinematerial, a distinct and abrupt change in the color of the selectivelyscattered light is observed. The greatest color change is observable inthe area of greatest mechanical force. A deformational force as small as0.5 gram per square centimeter can be registered as shear phenomenon byappropriate liquid crystalline materials. The sensitivity of thesematerials is illustrated by the fact that a liquid crystal encapsulationaccording to our invention and of suitable length tseveral feet, forexample) can be used to register a sound wave.

The color patterns produced by the deformational stresses have arelaxation time, that is to say the time for the visible effects of thedeformation to return to their relaxed" form after the deformationalstress is removed. The deformational stress is most advantageouslyapplied normally of the liquid crystal encapsulation. The pressure canbe applied for a smaller or greater interval of time, but preferably fora minimum of 0.2 second. The deformation stresses can be applied bymeans of an auxiliary member either incorporated in or separate from theencapsulation and having a message. aesthetic design, or the likeembossed thereon. A plurality of such auxiliary members can be provided,if desired, for use with a single encapsullation to provide a variety ofmessages or designs. By pressing the design or message member against aflexible portion of the liquid crystal encapsulation the message ordesign is delineated by lines or areas of darker color in the ensuingcolor pattern.

The clear or transparent member of the encapsulation can be made fromtwo or more associated materials of differing refractive indicies for afurther enhancement and a variety of the color pattern display.

Therefore, we also contemplate the use of various novel container meansto enhance or modify the color patterns and to protect the liquidcrystalline material from hostile environments. At least one section ofthe container is light-transmitting for viewing purposes and a secondcontainer section is secured thereto to enclose a quantity of the liquidcrystal. The second container section desirably is closely disposed tothe first-mentioned container section to conserve liquid crystallinematerial, which in most applications can be utilized in the context offilm thicknesses. The liquid crystal container can be substantiallyflat, or otherwise as described more fully below, and can be madesufficiently large to cover entire desk or table top surfaces or walland ceiling surfaces, for example. The liquid crystalling areas of suchpanels can be continuous or discontinuous depending on the applicationand character of the container. Light-absorbing means are associatedwith the liquid crystal material to absorb transmitted light, whichwould otherwise substantially mask that light which is also variablyscattered from the liquid crystal. The light absorber can beincorporated directly in the liquid crystal as a dark dye or suspendedmaterial. Alternatively, the second container section can be dark opaqueor otherwise dark hued to absorb part or all of the transmitted light toenhance the light scattering characteristic of the liquid crystallinematerial. Optimally the light absorber is black for maximum enhancement.At

least one of the container sections desirably is flexible or resilientso that the aforementioned deformational stresses can be applied to theliquid crystal externally of the package. Alternatively, deformationalstresses can be applied internally of the container, for example inaccordance with certain modifications of the invention described andclaimed in a copending, coassigned application of Edward N. Sharplessentitled Variable Color Display Device and Projection Means Therefor,"Ser. No. 40,899, filed concurrently herewith.

Desirably, the light-transmitting section is of a certain minimalthickness to enhance an illusion of depth in the color pattern of theliquid crystal. In such case, the light-transmitting panel preferably istransparent. The use of a relatively thick light-transmitting sectionfor enhancement purposes is particularly desirable in relatively smalldecorative objects or panels, which may be viewed from a number ofangles or positions. We also contemplate the formation of the liquidcrystal container in a variety of shapes and forms, for example as acube, parallelopipedon, prism, various types of pyramidal forms,hemisphere, hexahedron, octahedron, and other geometric forms. In themultifaceted fonns, we contemplate further the application of liquidcrystalline material and corresponding second container sections of twoor more faces or facets of the form. Obviously, the invention is equallyapplicable of nongeometric or random shapes which may be faceted ornonfaceted.

The aforementioned forms and shapes desirably are of lighttransmittingand preferably transparent material so that an in teresting array ofreflections and refractions of color patterns are seen within the shape.An unexpected feature of this form of the invention is the fact that thevarious reflections or refractions may be of widely differing basiccolors, as the viewing angle is effectively different for eachreflection or refraction of the liquid crystal surface. Our inventionutilizes, therefore, in an unobvious manner, another aspect of theselective scattering characteristic of the liquid crystalline material.

ln the latter feature of our invention the forms or shapes can be moldedfrom a transparent plastic and various types of coins, models, fossils,precious and semiprecious stones and the like can be molded within theplastic and viewed against the variable and colored background of theencapsulated liquid crystalline material. The last-mentioned displaydevices can be utilized as various decorative objects for desk and tabletops or as part of ink stands, pen and calendar holders and similarutilitarian articles.

in another arrangement of our invention, a synchronous motor can beprovided for operating the aforementioned stress-varying means inaccordance with a timed or rythmic sequence for synchronizing our colordisplay device with music or other rythmic operation. Our novel displaydevice is capable of an infinitely variable sequence of color patternsfor aesthetic, decorative, and entertainment purposes. A large number ofapplications of our inventions in the advertising field for varioustypes of eye-catching signs and displays will become readily apparent.

Our display device is capable of producing nonrepetitive color patternswhich are a mixture of natural hues and intensities. The effectsachieved are warm, relaxed, and psychologically subdued and aretherefore particularly desirable for decorative and other aestheticpurposes.

Besides its aesthetic values, our display device is useful in depicting,as a color display, relative motions between or among a number ofobjects. Such relative motions can be comparatively slight and even of avibratory nature. 0f greater significance is the capability ofsimultaneous indication of a number of forces applied externally to ourdisplay device at a given time.

We are aware, of course, of a number of United States Patents relatingto various applications of liquid crystalline materials. For example,Fergason et al., US. Pat. No. 3,l 14,836 depicts an imaging device,which exhibits a color pattern on a film of liquid crystal upon focusinga heat or thermal pattern thereon. Fergason US. Pat. No. 3,409,404discloses a liquid crystalline device in which variation in selectivescattering of liquid crystalline materials is employed for identifyingunknown materials. Williams US. Pat. NO. 3,322,485 utilizes a thresholdcharacteristic of liquid crystalline material to scatter lightselectively in the presence of a given electric field. Freund et al. US.Pat. No. 3,364,433 employs a frequency-shifting characteristic of liquidcrystalline materials in the presence of an electric and/or magneticfield. None of these references, however, discloses a color displaydevice utilizing liquid crystalline materials in which an infinite ornon-repetitive pattern is exhibited by a liquid crystalline materialapplied by attendant variation in applied mechanical stresses.

We accomplish these desirable results by providing a display device forexhibiting a color pattern, said device comprising container meanshaving a light-transmitting section and a juxtaposed opaque section, aquantity of liquid crystalline material interposed between saidcontainer sections and encapsulated within said container means, saidmaterial having a characteristic of selective light scattering within arange of temperatures at which said display device is normally utilized,and means for peripherally sealing one of said container sections to theother.

We also desirably provide a similar display device wherein said materialhas an additional characteristic of a selective light scattering whichis variable in accordance with applied deformational stresses, and meansare provided for the application of said deformational stress to saidmaterial.

We also desirably provide a similar display device wherein floweffecting means include means for displacing at least one of saidcontainer sections relative to the other of said sections to effect flowof said material within said container.

We also desirably provide a similar display device wherein thejuxtaposed surface of said opaque section is provided with a dark color.

We also desirably provide a similar display device wherein saidlight-transmitting member is a transparent hemispheroidal member, andsaid opaque container section is peripherally joined and sealed to asubstantially flat surface of said hemispheroidal member, at least someof the faces of said multifaceted member are disposed for reflectionand/or refraction of the color pattern of said liquid crystal.

We also desirably provide a similar display device wherein saidlight-transmitting section is a transparent multifaceted member havingcontainer means encapsulating a quantity of liquid crystalline materialand secured to at least one face of said multifaceted member.

We also desirably provide a similar display device wherein saidlight-transmitting section is a substantially flat transparent member ofabout one-eighth inch in thickness.

We also desirably provide a similar display device wherein saidlight-transmitting section in a transparent member and said opaquesection is peripherally sealed to a surface of said transparent memberto encapsulate said liquid crystalline material, a stand is provided forsaid display device, said stand being shaped to receive at least thoseportions of said transparent member adjacent said surface, said opaquesection is relatively flexible, and said stand includes indicia meansengageable with said opaque section when said device is seated in saidstand for applying deformational stress to said opaque section tooutline said indicia within a color pattern of said material which isvisible through said transparent member.

During the foregoing discussion, various objects, features andadvantages of the invention have been set forth, or alluded to. Theseand other objects, features and advantages of the invention togetherwith structural details thereof will be elaborated upon during theforthcoming description of certain presently preferred embodiments ofthe invention and presently preferred methods of practicing the same.

In the accompanying drawings we have shown certain presently preferredembodiments of the invention and have illustrated certain presentlypreferred methods of practicing the same, wherein:

FIG. 1 is an isometric view, partially broken away, of one form ofliquid crystal display device arranged in accordance with our invention;

FIG. 2 is a cross-sectional view of the device as shown in FIG. I andtaken along reference line II-II thereof;

FIG. 3 is a partial isometric view of another form of our novel displaydevice in conjunction with mechanical means for the application ofdeformational stresses;

FIG. 4 is an isometric view of still another form of our display deviceconfigured in the context of a common geometric form. Illustrated alsoare pressure-sensitive means for applying indicia to the liquid crystal;

FIG. 5 is an isometric view of still another form of our display deviceshowing a multifaceted and multicontainer geometric form;

FIGS. 6-8 are isometric views representing the incorporation of ournovel display device as still other geometric forms. FIGS. 7 and 8 showthe incorporation of other decorative objects within the liquid crystalcontainer structure;

FIG. 9 is a similar view of another form of our novel display deviceconfigured nongeometrically;

FIG. 10 is an isometric view of our novel display device incorporated ina surface of an article of furniture or the like;

FIG. 10A is an enlarged partial, isometric view showing a modified formof the light-transmitting member shown in FIG. 10;

FIG. 11 is a partial isometric view of one form of wall structureincorporating our novel display device;

FIG. 12 is an isometric view of another form of our novel displaydevice;

FIG. 13 is a cross-sectional view of the display device of FIG. 12 andtaken along reference line XIII-XIII thereof;

FIG. 14 is an isometric view of still another form of our novel displaydevice;

FIG. 15 is a similar view of still another modification of our displaydevice;

FIGS. 16 and 16A are top plan views of an advertising novelty arrangedin accordance with our invention;

FIG. 17 is an isometric view of a further modification of our displaydevice, arranged here as a paper weight or the like;

FIG. 18 is an isometric view of the modified form of the invention asshown previously in FIG. 15;

FIG. 18A is a cross-sectional view of the display device shown in FIG.18 and taken along reference line XVIIIA- XVIIIA thereof;

FIG. 19 is a similar view of another form of the novel display device;

FIG. 19A is a cross-sectional view of the device as shown in FIG. 19 andtaken along reference line XIXAXIXA thereof;

FIG. 20 is an isometric view of a further modification of the displaydevice of our invention;

FIG. 20A is a cross-sectional view of the device as shown in FIG. 20 andtaken along reference line XXAXXA thereof;

FIG. 21 is a similar view of a further modification of our novel displaydevice;

FIG. 21A is a cross-sectional view of the device as shown in FIG. 21 andtaken substantially along reference line XXIA XXIA thereof;

FIG. 22 is an isometric view of still another modification of ourinvention, presented here as a display device capable of exhibitingcolor patterns on both sides thereof;

FIG. 22A is a cross-sectional view of the display device of FIG. 22 andtaken along reference line XXIIA-XXIIA thereof;

FIG. 22B is a similar view of a modified form of the device as shown inFIGS. 22 and 22A, but incorporating novel message means;

FIG. 22C is a similar view of our novel display device but incorporatingmodified light absorption means, in which the color pattern is visiblethrough a flexible section of the display device container;

FIG. 22D is a cross-sectional view similar to FIG. 13 but illustrating asheet form modification of our invention, in which the display devicecontainer is completely flexible;

FIG. 23 is a side elevational view of a further modification of ournovel display device and incorporating another form of deformationproducing means according to our invention;

FIG. 23A is a cross-sectional view of the device as shown in FIG. 23 andtaken along reference line XXIIIA XXIIIA thereof;

FIG. 24 is an exploded isometric vrew of still another modification ofour novel display device;

FIG. 24A is an assembled isometric view of the display device shown inFIG. 24;

FIG. 24B is a cross-sectional view of the display device as shown inFIG. 24A and taken along reference line XXIVB- KXIVB thereof;

FIG. 24C is an isometric view similar to FIG. 22 and to others of thepreceding Figures. but illustrating the use of multiple encapsulations;

FIG. 24D is a cross-sectional view of the display device shown in FIG.24C and taken along reference line XXIVD- XXIVD thereof;

FIG. 25 is an isometric view of a modification of our novel displaydevice similar to that illustrated previously in FIG. 4;

FIG. 25A is a cross-sectional view of the display device as shown inFIG. 25 and taken along reference line XXVA- IKXVA thereof;

FIG. 25B is a similar view of a modified form of the display device asshown in FIGS. 25 and 25A;

FIG. 25C is a similar view of a modified form of the display device asshown in FIGS. 25 and 25A;

FIG. 25D is a similar view of a modified form of the display device asshown in FIGS. 25 and 25A;

FIG. 26 is an isometric view of still another modification of our noveldisplay device;

FIG. 26A is a cross-sectional view of the display device of FIG. 26 andtaken along reference line XXVIA-XXVIA thereof;

FIG. 27 is an isometric view of still another form of our hovel displaydevice;

FIG. 27A is a cross-sectional view of the display device as shown inFIG. 27 and taken along reference line XXVIIA- KXVIIA thereof;

FIG. 28 is an isometric view of still another form of our novel displaydevice;

FIG. 28A is a cross-sectional view of the display device as shown inFIG. 28 and taken along reference line XXVIIIA- KXVIIIA thereof;

FIG. 29 is a bottom plan view of a further modification of our noveldisplay device incorporating another form of our deformational means;

FIG. 29A is an elevational view, partly in section, of the displaydevice of FIG. 29;

FIG. 30 is an isometric view of still another form of our novel displaydevice, incorporating in this case novel illumination means therefor;and

FIG. 30A is a cross-sectional view of the display device as shown inFIG. 30 and taken along reference line XXXA- .KXXA thereof.

With reference now to FIG. I of the drawings, a display device I in thefonn of a liquid crystalline support 12 is illustrated therein. In thisarrangement, the support 12 in the form of a flat container havingopposed container wall sections or structures 14,16 of any suitable sizeand shape. In the arrangement shown, the wall sections l4, 16 aresubstantially coextensive although this is not an essential requirement.In point of fact, one of the wall structures 14, 16 can be significantlysmaller than the other wall structure (FIG. 3), as long as one wallstructure is joined about its periphery to the other wall structure, forexample in the manner described below. Likewise, the wall structures l4,16 need not be of flat configuration as illustrated but can be of someother configuration for example parallelopipedon or hemispherical asillustrated in FIGS. 4 and 5. It is contemplated however, that anygeometrical or nongeometrical, symmetrical or nonsymmetrical shape orform can be employed for either or both of the wall structures l4, 16.As noted previously, the wall structures 14,

16 need not be coterminus. Further, the wall structures I4, 16 need notbe planar as shown in FIGS. 1 and 2 but instead one or both sidesthereof can be dished as indicated in the aforementioned copendingapplication, or they can be otherwise configured as described below.

Depending on the manner in which the wall structures l4, 16 are joined,the resilience and hence the thickness of either or both of the wallstructures l4, 16 may or may not be critical. Such criticality, whetherencountered depends on the manner in which deformational stresses are tobe applied to a liquid crystalline material 18 confined between the wallstructures 14, 16. In the arrangement ofour novel display device asillustrated in FIGS. 1 and 2, at least one of the wall structures l4, 16is sufficiently thin or is made of a suitably plastic material as tolend a resilient or flexible character to the wall structure. Thus, thewall structure, such as the wall structure 16 can be bent or otherwisedeformed toward the wall structure 14 when a force is applied more orless transversely thereto as denoted by arrow 20. Such force can beapplied at various locations on the wall 16 as denoted by dashed arrows21.

By thus bending one of the wall structures l4, 16 relative to the other,the liquid crystalline material 18, which is supported, in this example,between the wall structures 14, 16 in filmlike form, is caused to flowgenerally away from the region of applied force (arrows 20, 21) to otherregions of the volume confined within the liquid crystal container 12.The application of the force 20 and the resultant flow of the liquidcrystal l8 develops shear and other deformational stresses within theliquid crystal 18. Such stresses modify the light scattering andattendant transmittance characteristics of the liquid crystal material18 and result in an endless variety of color changes and patterns.

In order to observe these aesthetic color changes one of the containersections, for example the section 14, is light transmitting, anddesirably transparent, to permit the display device 10 to be observedfrom a side away from the application of deformational forces 20 or 21.The clear container section 14 can be fabricated from polyacrylic,polycarbonate, polybutyrate, glass or other suitable material.

At least a portion of the other wall structure l6 can be made darkopaque or of a more or less transparent but darker hued material foroptimum visual characteristics, which result from viewing only the lightscattered from the display device 10, in particular from its liquidcrystal layer I8. The darker hued container section 16 may be a buffgray or other neutral color although desirably a darker coloration willmake the color patterns of a liquid crystal more obvious. A particularcolor may be selected or several colors can be provided on that side ofthe container section 16 facing the liquid crystalline material 18. Useof such coloring, particularly a darker color or mixture of colors,lends an interesting and subtle shading to the color patterns producedin the liquid crystals. For maximum light-scattering characteristics ofthe liquid crystal, the background coloration" desirably is black,which, as in the case of the aforementioned colors can be coated at 17on the container section 16 or incorporated therein. The termsdark-opaque" or dark-hued" are inclusive of black for the purposes ofthis specification and claims. Similarly, "darkhued" is inclusive ofcolored but transparent or translucent materials of low lighttransmittance. Desirably, whatever coloration is provided for thecontainer section 16 is made at least coextensive with the area of theliquid crystalline material 18. The dark colored, black and/or darkopaque layer can be applied at the interface of the liquid crystal 18and container section 16 as shown or alternatively on the juxtaposedouter surface of the container section 16, if the container section 16is otherwise clear or transparent. Alternatively the light-absorbingmeans can be physically incorporated in the liquid crystal 18, asdescribed below in reference to FIG. 22A.

As noted previously, at least one of the container sections l4, 16 isjoined about its periphery to a surface of the other wall structure. Inthe FIG. I arrangement, such joining means are further arranged toperipherally seal one wall structure to a surface of the other. In thedisplay device 10, such joining and sealing means include apressure-sensitive tape 22, which is compatible with the material of thewall structures l4, l6 and covers their coextensive peripheral edges.The liquid crystal 18 is thereby sealed in the context of filmthicknesses within the space defined by the slightly separated wallstructures 14, 16 and the peripheral tape 22. It will be understood, ofcourse, that the separation between the wall structures l4, 16 can bedifferent from that illustrated, depending upon the relative quantity ofliquid crystal 18 which is used, the desired intensity of colorpatterns, and the background coloration of the dark-opaque or dark-huedcontainer section 16. Generally, a relatively thin film of liquidcrystal 18 should be enclosed between the wall structures 14, 16 inconservation of the liquid crystalline material.

In those cases wherein the joining and sealing tape 22 is quite flexibleand more or less loosely applied at the wall edges or is at leastsomewhat elastic, one or both of the wall structures 14, 16 can be madethicker and hence less resilient. In such cases, an eccentricapplication of the deformational force 20 will cause one of the wallstructures to become slightly canted or angulated or otherwise displacedrelative to the other in order to induce deformational flows in theliquid crystalline material. Such deformational flows are, of course,aided by the elasticity and/or edge slackness of the joining and sealingtape.

In any event it is desirable to provide the light transmitting section14, particularly when transparent, with appreciable thickness to enhancethe variable color patterns of the liquid crystal l8 and to create anillusion of depth. When the display device is substantially planar as inFIGS. 1, 2, l and 11, the

, container section 14 should be in the neighborhood of about one-eighthinch or more in thickness although such thickness is not essential tothe invention and can be varied depending upon a specific application ofthe display device. When the device is incorporated into a relativelysmall decorative ob ject, a transparent container section of at leastthis thickness is desirable as the object is more readily viewed fromdifferent angles or positions. When supplied in greater thicknesses orwhen multifaced or faceted, the variable color display is even furtherenhanced as described below.

The liquid crystalline material 18 is selected from one or more of thosematerials which exhibit variation in light-scattering and attendanttransmittance characteristics under 'deformational stresses. Desirably,such variations are within the visible range at room temperatures or atwhatever ambient temperature conditions prevailing in the area ofutilization of the display device 10. As an example of the lattersituation, the liquid crystalline material 18 can be one of those whichexhibit visual stress variation in the aforementioned characteristics ator near body temperature, and is therefore useful when the displaydevice is held in the observer's hand. Larger display devices 10 can ofcourse be bathed with infrared radiation, if their liquid crystals arenot of the room-temperaturevisual variety. o

On the other hand, display devices for outdoor use, as for signs andother advertising situations, require liquid crystalline materialsexhibiting stress indicia at correspondingly lower temperatures.

There are a considerable number of substances which exhibit thecharacteristics required of the liquid crystalline material 18. Ingeneral the category of materials known as cholesteric liquid crystalsare suitable for use with my invention and exhibit an optical phenomenonknown as selective scattering of white light. The appellation ofthis'categorization of liquid crystals originates in the frequent use ofcholesterol as the starting material in synthesizing these organicsubstances. The derivatives of cholesterol usually are liquidcrystalline in character and demonstrate the characteristic of selectivelight scattering. Liquid crystalline substances fall additionally intothe general chemical classifications of esters, carbonic esters, ethers,schiff bases, and related classes.

Nominally, the cholesteric liquid crystals are not limited to the use ofcholesterol as a base material. Many steroids exhibit similar opticalcharacteristics when synthesized into the general classifications oforganic compounds, as mentioned above. These and other cholesteric"liquid crystals are useful for the purposes of our invention as long astheir molecular arrangement exhibits the necessary anisotropic andoptical characteristics.

For the purposes of our invention, we employ a cholesteric liquidcrystalline material which exhibits a relative optical phenomenonattendant to the selective scattering characteristic of this category ofliquid crystal. The latter characteristic is the stress or shearsensitivity of certain cholesteric materials whereby the selective(light frequency) scattering characteristic is varied upon theapplication of deformational stresses.

Cholesteric materials will selectively and visibly scatter white light,at or near room temperature conditions, when two or more of thesesubstances are admixed in proper proportions. Mixtures of liquidcrystals can be selected or varied to obtain visual responses at othertemperatures for the purposes mentioned previously. It is observed thata physical deformation of the liquid crystal will shift the frequency ofthe observed cholesteric color display or pattern, when viewed at agiven angle, toward the blue or shorter wave length end of the visiblespectrum. The amount of color shift, measured in wave length units, canbe employed to indicate quantitatively the physical stress applied tothe cholesteric material, when a given liquid crystalline material hasbeen properly calibrated.

A constant pressure applied to the liquid crystalline material will not,after its initial application, thereafter appreciably effect the thenobserved color patterns. Instead, the great variety of color changes orpatterns exhibited by our display device are produced by changes inapplied forces and attendant deformational stresses. With accelerationof changing deformational stresses, in either direction, changes in theobserved color patterns become more pronounced.

It has also been observed that the application of a constantdeformational stress over a significant period of time will initiallyinduce an observable change in the cholesteric color pattern, whichdespite continued stress, will revert to the unstressed or originalcholesteric color in time. That is to say, there is a relaxationaleffect in the liquid crystalline structure, owing to its nature.

It is contemplated that the liquid crystalline material may have asingle basic color or that a mixture of liquid crystalline materialshaving differing basic colors can be employed. For example, liquidcrystalline materials I, V, and/or Vl, tabulated below, can be employedin the package 10 or in others of the packages described below. It isalso contemplated that liquid crystalline materials of differing basiccoloration can be employed in differing areas of the package 10 butwithin the same liquid crystalline layer 18 to enhance the variety ofcolor patterns. Owing to the viscous nature of the liquid crystals, thediffering colored materials will not readily admix although the flexibleor resilient backing layer (if used) of the package is manipulated arelatively large number of times.

It will be understood herein that a cholesteric substance is one whichexists in the cholesteric state at a certain temperature. Thecholesteric state of such mesomorphic substance exists in the regionbetween the temperature at which the substance behaves as a true liquidand the temperature at which the substance is a solid. In thecholesteric state, the substance is optically negative, has a strongrotatory power, selectively scatters light to give vivid colors (ormonochromatic light to give areas of darkness and brightness), andexhibits circular dichorism. Such a physical state is especially notablein derivatives of cholesterol and like materials, although a relativelyfew other substances such as optically activeamylcyanobenzylidineaminocinnamate and the aforementioned steriodsexhibit the cholesteric state.

The liquid crystalline substances herein contemplated will be in thecholesteric state within at least a certain temperature Alan Ill

range, but as the temperature is raised above or depressed below thisrange the substances will pass into another mesomorphic state or into anormal liquid or solid state. Thus, the cholesteric substance will be inthe cholesteric state at a first temperature and will change its phaseinto some other state at a second temperature. The range of temperatureswithin which a visible color display is exhibited as a result ofscattering of white light can be determined by a proper selection ofcholesteric substances and will be referred to as the color play range.

Cholesteric substances used according to the present invention can bechosen from a wide range of compounds exhibiting the cholesteric phase.Derivatives of cyclopentanophenanthrene are desirably used. There are anumber of factors to be considered in selecting such derivatives: All ofthe ring systems should be in the trans configuration, the 3-:substituent (on the A ring) should be in the Bconfiguration, and thereshould be no more than two axial methyl groups. Unsaturation at the 5, 6carbon atom bond can have an effect on the melting point, but otherwisehas little effect on the formation of the cholesteric phase. Thus,derivatives of such cyclopentanophenanthrenes as cholesterol,compesterol, ergosterol, B-sitosterol, stigmasterol, and like materialscan be used.

llt is preferred in the present invention to utilize alkyl and arylderivatives of the cyclopentanophenanthrene materials, particularlythose derivatives which are esters of alkanoic or .aralkanoic acids, ormixed alkyl esters of the cyclopentanophenanthrene material and carbonicacid. The alkanoic acids used can contain from one to 24 or more carbonatoms in the molecule, and can be saturated or unsaturated and straightor branched chain. It is preferred to utilize esters comprising higherfatty acids, containing from nine to 22 carbon atoms or lower saturatedor unsaturated phenalkanoic acids having one to three carbon atoms.Mixed carbonate esters comprising alkanols having from one to 22 carbonatoms and cholesterol are also among the preferred cholestericsubstances.

Such derivatives of cholesterol are presently preferred in certainaspects of the invention. Thus, useful cholesteric substances includecholesteryl nonanoate. cholesteryl caprylate, cholesteryl laurate,cholesteryl palmitate, cholesteryl stearate, cholesteryl arachidate,cholesteryl behenate, cholesteryl ioleate, cholesteryl linoleate, andcholesteryl linolenate, cholesteryl benzoate, cholesteryl cinnamate,cholesteryl idihydrocinnamate, and the like. Carbonate esters such asoleyl cholesteryl carbonate, stearyl cholesteryl carbonate, methylcholesteryl carbonate, ethyl cholesteryl carbonate, pentyl cholesterylcarbonate, and the like carbonates are very useful in the presentinvention.

it will be appreciated by those skilled in the art that a purecholesteric substance may have only a very limited color play range.However, where this color change does not occur at the temperature ofinterest, several stratagems permit coverage of a broad range oftemperatures from C., and cven down to 40 C., up to and above 250 C. Onemethod of varying the color play temperature range is to prepare asubstance at a desired purity level, as increased impurities usuallylower the temperature range. One convenient method of carrying out thisadjustment is to admix a plurality of chemically distinct cholestericsubstances having different color play temperature ranges until thedesired temperature range is obtained. Another method of adjusting thecolor play range is to prepare the substance in a highly purified formand to admix enough of a less refined aliquot or aliquots of thesubstance with the purer material until the desired change of color playrange is obtained. For instance, in this latter aspect, a 99.99% purecholesteryl oleyl carbonate can be prepared and admixed with lessrefined material. Those skilled in the art will have no difficulty inproviding a desired transition temperature for use in the compositionsand articles of the present invention. All parts, proportions,percentages and ratios herein are by weight unless otherwise stated.

The following tabulation will exemplify a few of the many color playregions obtained with the cholesteric substance or substances:

90 0 10% cholesteryl benzoate Cholesteryl butyl carbonate- 20%cholesteryl dlhydroc1nnamate. cholesteryl nonanoate It will accordinglybe appreciated that one, two or more cholesteric substances can be mixedto obtain the requisite color play temperature range, and that both thetemperature and the range of temperatures can be widely varied. It isdesirable that the cholesteric substance(s) not crystallize at thelowest temperature at which they are held before use.

As disclosed above. a desired melting range can also be obtained byvarying the purity of cholesteric substances. It is usually found thatincreasing the purity raises the temperature of the color play regionand a narrowing of the range is also frequently obtained. It will, ofcourse be appreciated that the presence of excessive quantities ofimpurities will ultimately entirely prevent obtaining of the cholestericphase, especially if the impurities themselves are not cholestericsubstances. The cholesteric substance(s) can also comprise up to 5percent or so of miscible materials such as fatty acid triglycerides tolower the range. As disclosed hereinafter, it is most desira ble toprotect the cholesteric substance from the milieu to obviate theinhibition of impurities by the cholesteric substances and thereby tomaintain the desired color play temperature.

As an illustration, cholesteryl oleyl carbonate is prepared as describedin Detection of Liquid Crystals," AD 620 940, U.S. Department ofCommerce Aug. 1965). A portion of the cholesteryl derivative is purifiedby solvent extraction and washed with methanol. The purified cholesterylmaterial is found to have a color play temperature of 2 l-22 C. Admixing80 parts of this material with 20 parts of an unpurified materialprovides a color play temperature of 15 1 6 C.

The cholesteric materials for use with this invention can also include acholesteryl halide. Although cholesteryl fluoride can be prepared, thedesired halides for use herein are cholesteryl chloride, cholesterylbromide, cholesteryl iodide, and mixtures of these halides. Thepreferred halide for use herein is cholesteryl chloride.

The cholesteryl halide serves-to provide a uniform color over a broadrange of temperatures in which the cholesteric substance or substancesare in the cholesteric phase. Thus, in such case, our novel displaydevice shows a single color below transition to the condition whereinthe liquid crystal does not scatter visible light, i.e., the conditionin which it becomes colorless. The color below the transition point canbe selected according to the amount of cholesteryl halide used. As thequantity of halide is increased from about 15 percent of the compositionup to above 40 percent, the color usually varies from deep violet todeep red. The quantity of halide used will also vary according to theparticular cholesteric substances utilized.

These halides are conveniently prepared by refluxing the cholesterolwith an excess (twice or more, stoichiometrically) of a thionyl halidefor 48-72 hours and distilling the mixture thereafter to removeunreacted material. Generally, the purity of the halides is sufficientto permit the desired change of phase from the cholesteric. It ispreferred that the halides be at least 90 percent pure. Such halidesusually have a tendency to broaden the color play temperature range ofthe cholesteric substance(s).

Depending upon a particular application of our display device acholesterol halide may or may not be used depending on whether a singleor multiple color display is desired.

Specific examples of liquid crystalline compositions useful for ourpresent invention appear below, wherein all amounts are in parts, ChClis cholesteryl chloride melting at 9495 C.; High ChOlC" is cholesteryloleyl carbonate showing a color play at 20-22 C.; Low ChOlC" ischolesteryl oleyl carbonate showing a color play at -6 C.; ChNo" ischolesteryl nonanoate; and the upper temperatures are those at which thecompositions become colorless.

Color play High Low Example ChCI ChOlC ChOlC ChNo Color Range (0.")

Other alkanoic esters of cholesterol or alkyl carbonate esters ofcholesterol can be used in the foregoing Examples to provide a broadvariety of temperatures and temperature ranges for the liquidcrystalline material 18. Likewise, other cholesteric materials such ascorresponding derivatives of B- sitosterol, stigmasterol, ergosterol,and the like can be substituted with comparable results.

In the display device of FIGS. 1 and 2 it is contemplated that theforces 20, 21 can be applied manually, for example by pressing orstroking the container section 16 with the fingers. A single force canbe applied as designated by arrow or alternatively multiple forces canbe applied as desired as denoted by arrows 21. The edge-sealing tape 22can be of the pressure-sensitive variety, desirably of thelight-transmitting or transparent type, in the illustrate embodiment. Itwill be understood, of course, that other means can be utilized forjoining and sealing the container section 16 to the container section14. For example the joining means illustrated in the aforementionedcopending application or herein in subsequent figures can be utilized,depending upon the application of the invention.

Alternatively the container sections can be joined as illustrated inFIG. 3. The latter arrangement of our invention demonstrates also thatthe container sections need not be coterminus. In the container 12' ofthe display device 10 of FIG. 3, container section 16' is of appreciablysmaller area than that of the container section 14'. In this example thesection 14 is relatively rigid and light-transmitting or transparent incontrast to the resiliency and opaqueness of the section 16' for thereasons set forth above. Where the joining and sealing tape 24 is of acharacter, for example, inherent elasticity, to permit, of itself,relative displacement of the container'sections 14', 16', the containersection 16' can also be made rigid. The container sections 14', 16'enclose a quantity of liquid crystalline material 18' therebetween, andthe periphery of the smaller container section 16' (in this case) issealed and joined to the juxtaposed surface of the larger containersection 14', by means of the aforementioned tape 24. The tape 24 also isof the pressure-sensitive variety, and can be light-transmitting ortransparent to render its presence less obvious. The structure of FIG. 3exhibits the practical ad vantage of an inobvious joining means, whenthe display device 10' is viewed from its light-transmitting surface.

The color patterns of the liquid crystal 18' can be varied manually inthe manner set forth above with respect to the display device 10 ofFIGS. 1 and 2. Alternatively, various mechanical means can be providedin conjunction with the display device 10' for the application ofdeformational stress of the liquid crystal 18'. One form of such meansincludes contacting means 26 including in this example roller 28positioned to engage the external surface of the opaque wall structure16'. Means are provided for reciprocating the contacting device 26-28across the exposed surface of the container section 16'. One arrangementof such means includes a link 30 pivoted at 32 to the contacting means26 and to crank 34. Although the crank 34 is illustrated for manualactuation by hand wheel 36, suitable motive means (not shown) can besubstituted. The roller 28 of the contacting device is held in bearingengagement with the container section I6 by means of a pair of slottedbrackets 38, 40 which engage the projecting ends 42 of the roller axle.

The varying color patterns of the display device 10' can be set to musicor other rhythmic activity by rotation of the crank 34 in accordancewith a predetermined timed sequence, as by use of a synchronous drivemotor (not shown) and suitable gearing or other transmission,arrangements of which are disclosed in the aforementioned copendingapplication.

The force applying arrangement of FIG. 3 is particularly useful forvarying the color patterns of large-area devices such as the wall panelillustrated in FIG. 11 or other relatively nonportable display devices.

xsbdiiiiea' out in the description of FIGS. 1 and 2 and previously it iscontemplated that the light-transmitting or transparent containersection can be provided with appreciable thickness to enhance thevariable color display made possible by our device. For example displaydevice 44 of FIG. 4 is furnished in the form of a container 46 includingin this example a hemispheroidal container section 48 and asubstantially flat container section 50 adhered to the flat face 52 ofthe container section 48. In the modification of FIG. 4 thesubstantially flat container section 50 can be applied as shown in FIG.3 except that the container section 50 desirably is made circular. Thehemispheroidal container section 48 provides an interestingmagnification and refraction of color patterns 54 of the liquidcrystalline material enclosed between the fiat face 52 of thehemispheroidal section 48 and the flat container section 50.

The display device 44 can be utilized, for example, as an entertainingand ornamental novelty for a table or desk top. A relatively slightpressure upon the rounded surface of the hemispheroidal containersection 48 will apply compressional forces to the resilient ordisplaceable container section 50 resting, for example, directly uponthe table or desk top. This in turn will cause various flow patternswithin the liquid crystal 54 depending upon the magnitude and locationof the applied forces. As a result an interesting and entirelyunexpected variable color display is produced.

We contemplate also that localized forces can be applied to the externalsurface of the container section 50. One arrangement for effecting suchforce application includes a stand 56 adapted for the display serve 44and likewise shown in FIG. 4. The stand 56 in this example includes aretaining rim 58, shaped to receive the peripheral surface of thedisplay device 44 adjacent its flat face 52. The bottom of the stand 56desirably includes a number of contact surfaces arranged in the form ofa design, message, various geometrical configurations, or other indicia.For example, the bottom area 60 of the stand 56 may incorporate theowners initials denoted in this example by reference numeral 62. Thedesign, message item, or indicia 62 can be fabricated from any suitablestructural material, plastic or metallic, and desirably are arrangedsuch that their undersurfaces seat flushly against the table or desktop. The upper surfaces of the design or message items 62 projectsufficiently above the remainder of the bottom structure 60 and aresupported in this example by connecting links 64. In consequence onlythemessage items 62 are engaged by the container section 50 when thedisplay device 44 is seated in the stand 58. When so arranged themessage items or indicia 62 depress the flexible container section 50 attheir top surface areas with the result that the items appear as adiscrete and contrasting coloration within the color pattern 54 of theliquid crystal. A variety of stands 58 can be furnished with a tingledisplay device 44 to display a variety of message or design motifs ofthis character. When the several stands, similar to the stand 56. arethus changed corresponding changes in the overall color patterns of theliquid crystal patterns likewise occur owing to difiering distributionof applied base or bottom forces at the flexible container section 50.

Other geometric shapes can be utilized in addition to the hemisphere orhemispheroid of FIG. 4. For example, FIG. illustrates another geometric.transparent member 66, exemplarily in the form of a cube, forming partof display device 68. One or more faces of the cube 66 can be utilizedas a component container section of a corresponding number of liquidcrystal containers or cells. In the illustrated display device 68 twosuch cells 70 are afforded, although obviously a different number can befurnished. Each of the cells 70 include, in this example, asubstantially flat container section or structure 72 of about the samesize as the adjacent face of the cubic member 66. The containerstructures 72 can be secured to the corresponding face of the member 66by means of pressuresensitive tape 74, after the manner of FIG. 3 orFIG. I depending upon whether the container structure 72 is desired tobe of the same size (FIG. I) or correspondingly smaller than thejuxtaposed face of the cubic member 66 (FIG. 3). Quantities 76 of liquidcrystal enclosed between the container sections 72 and the juxtaposedfaces of the cubic member 66 are visible within the transparent cubicmember 66. The facets or faces of the cubic member 66 provide aninteresting array of reflections and refractions of the variable colorpatterns of the liquid crystal portions 76. With only a liquid crystalencapsulation at only one cubic face. for example. up to about I3reflections and refractions (including secondary images) can be seen. Anendless variety of color patterns, therefore. can be obtained byapplication of forces to the container sections 72 after the manner ofFIG. 2 or FIG. 3. or as set forth in the aforesaid copendingapplication. and/or by changing viewing angles.

Similar geometric shapes are illustrated in FIGS. 6. 7 and 8 whichrespectively show parallelopiped. pyramidal, and prismatic shapes. Thetransparent members 78. 80 and 82 of these figures each have liquidcrystalline material 84. 86 or 88 confined against one face thereofafter the manner of FIG. 4 pr FIG. 5. Liquid crystalline material (notshown) similarly can be applied to additional faces of each transparentmember 78. 80 or 82 if desired. The display devices 90. 92, 94 of FIGS.6-8 provide interesting and respective arrays of reflections andrefractions of the color patterns of the contained liquid crystallinematerial. For example in FIG. 6 the several refractions and reflectionsof the liquid crystal patterns are denoted by the reference characters84' and will of course vary depending upon the direction from which thedisplay device 90 is viewed. Similarly, refractions and reflections 86'appear in the display device 92 of FIG. 7 and a reflection 88' in thedisplay device 94 of FIG. 8. These and additional reflections andrefractions will appear or disappear depending upon the viewing angle,all of which heightens the interest engendered by the display devices.Moreover. the basic color of the associated liquid crystal pattern andits reflections and/or refractions will vary depending on the viewingangle. Of equal importance, the several reflections and/or refractionswill differ in color from each other and from that of the liquid crystalitself, as the viewing angle is effectively different for eachreflection or refraction, although the display device is viewed from asingle position.

The aforementioned liquid crystal color patterns (which can be varied bythe application of deformational stress as described previously or asset forth in the aforementioned copending application) can be employedas unexpectedly decorative and entertaining backgrounds for items suchas coins, models, fossils. precious and semiprecious stones. specimensand the like embedded in the transparent member. In furtherance of thispurpose a molded plastic such as plexiglass or one of the polyacrylicresin is employed for the transparent member. In the display devices 92and 94 (FIGS. 7 and )8) coins 96 and 98 are so used. Other items (notshown) can be employed with or substituted for the coins 96, 98. In FIG.7. one such coin 96 has been molded within the transparent member 80.while several coins, in differing positions have been so included inFIG. 8. A reflection 96 (FIG. 7) or reflections of these items mayappear depending again on the viewing angle.

The display devices according to this feature of our invention are notlimited, of course, to geometric shapes. For example display device I00of FIG. 9 incorporates a faceted but nongeometric or irregulartransparent solid 102 against at least one face or facet of which iscontained a quantity of liquid crystalline material. The last-mentionedliquid crystalline material preferably is encapsulated against thejuxtaposed facet of the transparent member 102 in the manner describedpreviously. A color pattern 104 of the liquid crystal appears in anumber of additional faces 104 of the transparent member I02. The shadedfacets 106 denote areas of mirror-type reflections. which, when combinedwith the liquid crystal color pattern I04 and its various reflections orrefractions 104', again provide an unexpected decorative andentertaining display.

The display devices of FIGS. 4-9, as in the case of the devices 10 and10 of FIGS. 1-3 are made of any convenient or suitable size. Primarily.the display devices of FIGS. 4-9 are intended for relatively smallornamental items for various decorative purposes.

In FIG. 10, however. the adaption of our novel display device torelatively large surface areas is exemplified. The latter form of ourdisplay device 108 is incorporated in an article of furniture. in thisexample table 110. For maximum effect the display device 108 is appliedto top structure 112 of the table 110. The display device 108 furtherincludes a lighttransmitting member 114 which conforms in contour andextent to the shape of the table top I12. The table top 112 and thelight-transmitting member 114 are flat although this is not necessarilythe case.

A quantity of liquid crystal 115 is enclosed between thelight-transmitting member or sheet 114 serving as one containercomponent and a preferably opaque structure including sheet I16 whichserves as the other liquid crystal component. The sheet 116 is adheredabout its peripheral edges to the undersurface or periphery of thelight-transmitting member I I4. The sheet 116 can of itself be opaque,or if transparent, the table top 112 preferably is opaque.

The container components 114, 116 can be secured and sealed togetherafter the manner of FIGS. 1 or 3. Desirably also the light-transmittingor transparent member 114 is relatively thin such that forces applied tothe upper surfaces thereof. either manually as by individuals utilizingthe table for various purposes or by various utilitarian objects placedupon the light-transmitting member 114, produce an endless andunexpected variety of color patterns within the liquid crystallinematerial as a result of its variable lightscattering andpressure-sensitive characteristics.

To heighten the observers interest still further a lens or refractiveconfiguration I18 can be molded in the light-transmitting sheet 114 ofthe display device 108', as shown alternatively in FIG. 10A.

The display arrangement 108 or 108' can, as noted previously, be appliedto other furniture surfaces. disposed either vertically or horizontallyor at some other inclination as desired. An interesting application ofthis arrangement of our invention is to a piano top (not shown) or othersurface subject to sonic vibrations. Alternatively, a display device,such as the device 108 or 108' can be stretched over a loudspeaker cone(not shown) in an analogous arrangement. In this latter application thedisplay device including its container components desirably is maderelatively thin for maximum sensitivity of the liquid crystal containedtherebetween to sonic vibrations. Other applications subject tovibratory forces will suggest themselves.

The display device as shown in FIG. 10 or 10A can likewise be applied toroom surfaces and for this purpose can be furnished in the form ofconveniently sized panels fabricated after the manner of the displaypanel 108 or 108' in FIG. or 10A. These can be applied to floor, wall,ceiling and/or door surfaces of a conventional room or as a stage orauditorium backdrop. One arrangement of such panels is illustrated inFIG. 11, where display device 120 is shown as a wall panel and will bepresently described. Deformational forces can be applied to theaforementioned panels by manual pressures exerted against the accessiblesurfaces of the panel, or by mechanical means such as illustrated inFIG. 3 in this application or in various Figures of the aforementionedcopending application With the incorporation of display device 120 in aroom structure as shown in FIG. 11, the device 120 desirably includeslight-transmitting sheet 122 which preferably faces the interior 124 ofthe room structure 126. The sheet 122 can be provided with cove I28,baseboard 130 and base shoe 132 moldings where appropriate to conform toconventional wall structures which may be used elsewhere in the room.The light-transmitting panel 122 can be secured to studs 134 or otherstructural members conventionally used in bearing and nonbearing wallsas the case may be.

The rear of the light-transmitting panel 122, i.e., the side away fromthe interior 124 of the room structure 126, is substantially covered byencapsulating means for retaining a relatively thin layer of liquidcrystal against the rear surface. In the illustrated arrangement theencapsulating means are extended generally between adjacent pairs of thestuds 134 or other wall support members. One form of such encapsulatingmeans includes one or more container sections 136 secured to the rearsurfaces of the light-transmitting panels 122 and disposed between eachassociated pair of the studs 134. In the illustrated example three suchcontainer sections 136 are utilized between each pair of studs, althougha different number can be employed.

The container sections 136 desirably are relatively stiff but resilientplastic sheets adhered about their peripheries to the juxtaposedsurfaces of the light-transmitting panel 122 after the manner of FIGS. 1and 3 and related figures described above, or after the manner of FIGS.12-16 described below. The container sections 136 can be colored orcoated as described previously and each encloses a quantity of liquidcrystal against the adjacent surface of the light-transmitting panel122. Any rear surfaces of the light-transmitting panel 122 which are notcovered by the container sections 136 can be suitably masked by varioustypes or colors of coatings. For example, the masked areas, such asdenoted by reference characters 130, can be colored to blend more orless with the color patterns produced by the several liquid crystallineareas as defined by the container section 136 and visible through thefront surfaces of the light-transmitting Another arrangement of ournovel display device is exemplified by display container 140 of FIGS.l2, 13. The display container 140 or aesthetic novelty includes alight-transmitting member 142, which can be fabricated from apolyacrylic resin in sufficient thickness to give the aesthetic novelty142 sufficient rigidity or structural strength. For example, if theaesthetic novelty 140 is of the order of about 4 inches square, thelight-transmitting member 142 can be of the order of about one-eighthinch in thickness, although a greater or lesser thickness can beemployed as evident from FIGS. 16, 16A described below. Desirably, thelight-transmitting member 142 is fabricated from a fully transparentpolyacrylic resin to enhance the color patterns of the liquid crystalmaterial 144 encased between the light-transmitting member 142 and adesirably darker-hued or dark-opaque film or sheet 148 adhered to theupper surface (as viewed in FIGS. 12 and 13) of the flexible film 146.Other light-absorbing means can be substituted such as described withreference to FIG. 22A and other figures hereof. In this arrangement, thefilm 146 can be formed from a sheet of PVC plastic or the like to whicha coating of pressure sensitive adhesive is applied entirely over onesurface thereof. The PVC sheet or film 146 and the application of theadhesive thereto can be formed by conventional techniques.

The area occupied by the liquid crystalline material 144 can bedemarcated by a sheet of heavy paper or cardboard or by a second plasticfilm or sheet 148, which can be pressed into adhesive engagement withthe central area of the adhesive film 146. Use of the film layer 148prevents the juxtaposed surfaces of the film 146 from adhering to theunderside of the light-transmitting member 142 and thus delineates ashallow pocket for the liquid crystalline material 144.

The film layer 148 can be coated or formed from a material having a darkor other contrasting color relative to the predominating color of theliquid crystalline material 144. Printed messages (not shown) or variousdesigns, e.g., the design 150 (FIG. 12) or 152 (FIG. 14) or 154 (FIG.15), can be applied to the film or sheet layer 148. Such designs, forexample the designs 150, 152 can be printed in darker colors or shadesupon a light background or alternatively as evident from the design 154in FIG. 15, the design can be delineated in lighter colors against adarker background. Also, the designs can be more or less geometrical asshown in FIG. 12 or random as shown in FIG. 14 or pictorial as shown inFIG. 15. The unique cooperation of the contrasting colors of the filmlayer 148, when provided with a design of some sort such as thosedescribed above, is evident when the flexible film 146 is depressed inthe area of the film layer 148 to apply deformational stresses to theliquid crystalline material 144. The alternate thinning and thickeningof the liquid crystalline layer considerably enhances the varying colorpatterns resulting from deformational flows in the liquid crystal.Interest in the liquid crystalline patterns is heightened, with thevariation in thickness or depth of the liquid crystalline material abovethe various contrasting colors or shades of the designs imparted to thefilm layer 148.

The area of contained liquid crystal, such as the area 156 in FIGS. 12,13 can be similar in shape to that of the light-transmitting member 142or can be of a different shape or series of shapes (not shown) asdenoted by the liquid crystal areas 158 of FIG. 14 or 160 of FIG. 15.Similarly, the light-transmitting member 142 of FIGS. 12-14 can be ofgeometrical contour or can be of some other contour as denoted by thelight-transmitting member 162 of FIG. 15. The film 164 adhered to thelight-transmitting member 162 desirably is of similar shape.

It is contemplated that the film layer 148 can be omitted, and that theaforementioned pressuresensitive adhesive layer can be confined to theperipheral areas of the film 146 or 164 to delineate the containersections or areas 156, 158, 160 of FIGS. 12-15 respectively. In suchcase, the designs 150, 152 and 154 can be printed or embossed directlyupon the uncoated central areas of the films 146 or 164. As a furtheralternative either the film layer 148 (FIG. 13) or the central region ofthe films 146 or 164 can be coated or otherwise provided with auniformly dark or black material for a uniform enhancement of the liquidcrystalline color patterns, as mentioned previously. Alternativelyagain, the designs I50, 152 and 154 of FIGS. 12-14 can be replaced withrandom color patterns, or with messages of various kinds printed incontrasting colors or shades upon darker-hued or opaque films I46, 164,or on the overlying film layer 148, when used (FIG. 13), or on thetransparent member 142.

As a further enhancement of the color pattern variation and interesttherein, an air bubble 166 (FIG. 12) can be introduced into the liquidcrystal area 156, along with the liquid crystalline material. The airbubble 166 operates to thin the juxtaposed portions of the containedliquid crystalline material, and such thinning provides an interestingvariation in the resulting color patterns. Also. interesting differencesin reflection occur at the air bubble, depending on viewing angle. Inaddition, as the flexible backing member 146 is depressed ordeformational stresses are otherwise applied thereto, the bubble 166tends to break up into a number of smaller bubbles exhibiting variablepatterns, depending on the amount and area of pressure application, tofurther increase the viewers interest in the color patterns. The use ofthe bubble 166 is particularly fascinating in conjunction with theaforedescribed designs I50, 152, I54 and equivalents, as the presence ofthe air bubble enhances the delineation of those portions of the designwhich are juxtaposed thereto. The correspondingly thicker regions of theliquid crystal 144 removed outwardly from the bubble I66 tend to subduethe design delineations. The sharper delineations of the design 150 aredenoted in FIG. 12 by shaded areas 1500 of the design 150. The airbubble 166, whenever broken up into a number of discrete smaller airbubbles, tends to reform as a single air bubble after removal of thedeformational stresses. Similar air bubbles 168 (FIG. 14)

*and 170 (FIG. 15) can be employed in conjunction with the designs 152and 154 of these figures respectively. The air bubbles 166-170 can be ofdiffering relative sizes than as illustrated, as long as the areanormally occupied by the bubble is substantially smaller than that ofthe liquid crystal.

In FIGS. 16 and 16A, another form of our novel color display device 172is illustrated with optional commercial aspects. The display device 172can be fabricated from relatively thin material, for example in theshape of a calling card or the like. In this case the liquid crystallinematerial 174 is encapsulated between a darker hued or opaque film 176and a light-transmitting or fully transparent film 178, which areotherwise assembled after the manner illustrated in FIG. 13 or inaccordance with the encapsulating technique described and claimed in aeopending, coassigned application of Frederick Davis filed Mar. 19,I969, Ser. No. 803,319 entitled Thermometric Articles and Methods forPreparing Same." The liquid crystalline material 174 can be selected toexhibit the requisite color play temperature at room temperature as inthe case of the display devices described previously. In that case thedisplay device 172 will normally exhibit the appearance of FIG. 16A. Itwill be understood, of course, that some other design motif can besubstituted in place of the spherical portions 180a, 180b and thecommercial message 1800, all of which are delineated by the encapsulatedliquid crystalline material.

Alternatively, and to add a note of intrigue to the brilliant colorpattern of the liquid crystalline material 174, the liquid crystallinematerial can be selected with a different color play temperature range,in the manner discussed previously, commencing above the normal roomtemperature range but, for example, below the temperature of the humanbody. Thus, the liquid crystalline pattern will assume the base color ofthe base film 176, which desirably is made a dark color or black forthis purpose. In consequence, the display device 172 will assume auniform dark or black color as evident from FIG. 16, against which thedelineations of the liquid crystalline material (shown in dashed outlinein FIG. 16 for illustrative purposes) are not visible at all, until thedisplay device 172 is warmed to the requisite color play temperaturerange, for example by holding in the individual 5 hand.

A further modification of our novel display device 182 is shown in FIG.17 and is arranged in this example as a largely transparent novelty suchas a paper weight or the like. The display device 182 includes in thisexample a solid block 184 of transparent material, such as one of thepolyacrylic resins. The transparent block 184 is provided in accordancewith this aspect of our invention with a first embedment 186 of liquidcrystalline material and a second embedment 188 of a design or letteringsuch as a slogan, motto, the owner's name or initials or the like. Thesecond embedment 188 can be formed in the transparent block 184 forexample by printing or lettering the design or message with opaquedark-hued ink on a transparent support or a support of darkertransparent hues, as required.

The liquid crystalline embedment 186 can be provided after the mannerdescribed in connection with FIGS. 16, 16A with the exception that twotransparent films are employed to permit viewing of the second embedmenttherethrough. The first embedment 186, as in the case of the second orconventional embedment 188, can then be suspended within the transparentblock 184, when the latter is molded, by conventional techniques. Whenthe liquid crystal embedment 186 is viewed through top face 190 of thetransparent block 184 the design or message of the second embedment 188is viewed through the color display afforded by the color patterns ofthe liquid crystalline material located in the first embedment 186. To

enhance the color display, the bottom face 192 of the transparent block184 can have a relatively dark hue, or a black coating can be applied.Alternatively the design or message of 5 the second embedment 188 can beapplied in lighter colors against a darker background, which can beopaque or more or less transparent as desired.

Means, (not shown) can be provided for the application of deformationalstresses to the first or liquid crystal embedment 186, for example inaccordance with the teachings of a copending and coassigned applicationof Edward N. Sharpless, filed concurrently herewith entitled VariableColor Display Device and Projection Means Therefor, Ser. No. 40,889. Inthe absence of such deformational means, the liquid crystal embedment186 still yields an interesting variety of color patterns depending, forexample, upon the character of light falling upon the transparent block184, incident angle ofillumination, and individual viewing angles.

It is contemplated further that the liquid crystalline material 186 canbe embedded by forming the insulating block 184 from bipartitetransparent container sections, which are shallowly dished toencapsulate the liquid crystalline material 186 therebetween. Thebipartite transparent member can be permanently joined after the liquidcrystalline material 186 is injeeted therebetween, by heat or solventwelding, use of adhesive or cement, etc.

From FIG. 18, it is apparent that our novel display device 190 issimilar to that of FIG. 15, in that a design, message, logo, artwork, ortrademark 192 is incorporated in the package 190 and juxtaposed to thelight-absorbing means 194 (FIG. 18A) thereof. Liquid crystallinematerial 196 is encapsulated after the manner of FIG. 13 between arelatively rigid transparent member 142 and an adhesive sheet 146. Thelight-absorbing member 194 which is, in this example, adhered to theadhesive sheet 146' to define the encapsulating area of the displaydevice 190 is a transparent plastic sheet of polyvinyl material having aphotoemulsion 198 thereon.

The emulsive layer 198 is exposed save for the areas defining the logoor other mark 192. The transparent areas 192 in the absorption means 194provide a considerably enhanced delineation of the design, advertisingmessage, logo, or the like 192 of the display device 190. This followsfrom use of a somewhat translucent adhesive sheet 146' such that alimited amount of transmitted light passes through the liquidcrystalline material 196 at the transparent areas 192 in the absorptionmeans 194. Other arrangements can, of course, be employed to enhance thedesign 192 by affording a limited light transmittance, for example, thatdisclosed in FIGS. 24, 24A and 24B described below.

A modification of the message means of FIG. 18 is illustrated by thedisplay device 200 shown in FIGS. 19 and 19A. The display device 200 canbe assembled in a similar manner, save that the light absorption meansor sheet or film 202 is uniformly black or dark-hued. A message ordesign bearing member 204 is suspended within the body of the containedliquid crystal 206. As better shown in FIG. 19, the suspended member 204can carry a design, logo, or message 207, which can be commercial orotherwise. The message 207 can, for example, be displayed against abackground area 208 of the suspended member 204, which background can bethe same, or a different color or texture from that of the lightabsorbing member 202. In the event that the suspended member 204 isprovided with a dark or black background, the member 204 itself becomesan auxiliary light absorbing means.

In the package 200, depending upon the basic color of the liquid crystal206 being utilized and on the color of the message or design'207, theliquid crystal material may partially or completely obscure the message207 when the display device 200 is in its quiescent state. That is tosay, the suspended member 204, fabricated in this example from a pieceof polyvinyl plastic sheet, will gradually settle to the bottom of thedisplay device 200, Le, against the light absorption means 202 thereof.Under these conditions, a substantial thickness of the liquid crystal206 covers the message or design 207. With this construction, themessage or design 207 only becomes evident when the flexible containerportion 146' is depressed to move the suspended member 204 against thejuxtaposed face of the relatively rigid container member 142'. Thisobscuration is enhanced by making the same color as the basic colorationof the liquid crystal. The design, then, becomes evident when the angleof incident illumination is changed, which changes the apparent basiccoloration of the liquid crystal. Alternatively, the message or design207 can be made more or less evident, as the case may be, bymanipulating the container section 146' to position air bubble 210 overthe design or message 207 or to displace the bubble 210 therefrom.

We contemplate, of course, that the package or display deviceconstruction of FIGS. 18, 19 and related figures need not be confined toflat or planar display devices. For example a display device of FIGS.20, 20A demonstrates the principles of our novel container constructionas applied to a hollow, cylindrical display device 212. In thisarrangement, the display device 212 includes an outer cylindricalcontainer section 214 of a clear or transparent material such as glassor polyacrylic resin. An inner container section 216 is formed from arectangular sheet of a suitable plastic coated with pressure sensitiveadhesive. The inner container section 216 can be rolled as better shownin FIG. 20A and lapped at 218. The major portion of the containersection 216, in this example, is covered with a rectangular sheet 220 oflight-absorbing material of a black or dark hue. The light-absorbingsheet can be likewise rolled and lapped, as denoted at 222.

A quantity of liquid crystal 224 is inserted between the light absorbingsheet 220 and the juxtaposed surfaces of the cylindrical outer containersection 214. The sheet 216 desirably is provided with a coating ofpressure-sensitive adhesive for adhering to the inner surfaces of theouter container section 214 adjacent the ends thereof as denoted byreference characters 226, 228 respectively (FIG. 20). Desirably, theinternal diameter of the display device 212 is sufficient to affordaccess to an individuals finger or other means for applyingdeformational stresses to the flexible container section 216.

Alternatively, the flexible container section can be of clear materialand applied to the exterior of the tubular member 214 after the mannerof FIGS. 22, 22A. In such case, the liquid crystal 224 can be providedwith a contained light-absorbing means as described below in connectionwith the latter figures.

Still other forms of hollow display devices can be made after the mannerof the display device 230 illustrated in FIGS. 21-21A. In thisarrangement, the display device 230 includes a container section 232 ofexemplary, pyramidal configuration, although a differing geometric ornongeometric shape can be utilized. One face of the pyramid shape 232,for example the bottom face, is provided with a liquid crystal package234, of which the adjacent surface of the pyramidal shape 232 forms apart, after the manner of FIGS. 6-9. Alternatively, two or more liquidcrystalline packages can be provided after the manner of FIG. 5. Theprecise construction of the liquid crystal package 234 can be modifiedin accordance with one of several of the accompanying figures, forexample after the manner of FIG. 22A or 228, substituting, of course,the pyramidal shape of FIG. 21 for the planar, rigid member of thelatter figures.

The several reflections and refractions within the transparent pyramidalshape 232 are multiplied by the provision of a hollow core 236 withinthe solid transparent member 232. The core 236 can be sealed as shown inFIG. 21 or in the alternative conduit means 238 and 240 (FIG. 21A) canbe coupled thereto.- In any event, the core 236 can be filled with a gasor liquid having a differing refractive index from that of the materialcomprising the transparent block 232. The differences in refractiveindices and the several interfaces between the gas or liquid within thecore 236, multiplies the number of reflections and refractions of theliquid crystalline pattern 238 and enhances the visual aspects of thedisplay.

For further variety and enhancement of interest in the display device230, we contemplate the partial filling of the core 236 as denoted bychain line 240 in FIG. 21A. In such case, the core 236 contains a liquidportion 242 with an air pocket 244 thereover. Alternatively, the airpocket 244 can be replaced by an immiscible liquid portion having alower specific gravity than that of the liquid portion 242. For furthervariety in interest, the liquids 244 and 242 can be dyed with differingcolors.

FIG. 21A also illustrates alternative means for filling or changing orcirculating the fluid or fluids contained within the hollow core 236.Such means includes the aforementioned connecting conduits 238, 240, apump 246 and suitable connecting conduits. Valved conduit sections 248,250 can be coupled to a suitable source or sources (not shown) ofappropriate fluids for filling the core 236. In the event that the core236 is filled with two liquids 242, 244, the core can first becompletely filled with the lighter liquid 244, from which subsequently aportion is displaced by circulation of a heavier liquid 242, to providea liquid-liquid interface (chain line 240).

Another arrangement for packaging liquid crystalline materials fordisplay purposes is illustrated by display device 252 in FIGS. 22, 22A.In this modification of our invention, the display device 252 exhibits avariable color pattern of liquid crystal 254 from both sides of thedevice 252. This is accomplished by utilizing a relatively rigid lighttransmitting or clear container section 256 and a resilient or flexiblecontainer section 258 of light-transmitting or clear plastic 258. Aperipheral portion of the plastic sheet 258 is provided with pressuresensitive adhesive at 260 for peripheral sealing of the sheet to thecontainer section 256 to encapsulate liquid crystal 254 therebetween.The liquid crystal 254 desirably is of the pressure-sensitive varietydescribed previously.

To permit viewing of the color pattern of the liquid crystals fromeither side of the display device 252, under normal conditions andwithout the use of auxiliary viewing devices such as crossed nichols, wehave unexpectedly found that light-absorbing means can be incorporatedwithin the liquid crystalline material 254. Such light-absorbing meanspermit viewing of the liquid crystal patterns from either side of thedevice 252 by means of variably scattered light from the liquidcrystalline material, while eliminating all or a substantial portion ofthe otherwise interfering transmitted light.

One form of such light-absorbing means includes the use of a black ordark-hued dye, for example a nigrazine dye. The nigrazine dye ismiscible with the liquid crystalline material 254 and can be used in therange of about two percent to about 10 percent by volume. Alternatively,the light-absorbing means can comprise carbon black or other finelydivided light absorbing material suspended within the liquid crystal, inan amount (in the case of carbon black) of from about I to about 30percent by weight.

Another form of our display device 262 is illustrated in FIG. 228. Thedisplay device 262 presents a variable color pattern visible throughflexible container section 258, which in this case is a transparentplastic sheet material such as Mylar. The other container section 256,which in this example is more or less rigid, is likewise transparent.The package 262 as described thus far is assembled after the manner ofthe display device 252 of FIG. 22A. To facilitate assembly a nonadhesiveclear plastic sheet 264 can cover a central portion of the adhesiveclear sheet 258' to demarcate the area occupied by the liquid crystal266. In the case of the display device 262, however, the liquidcrystalline material 266 does not have a selfcontained light-absorbingmeans such as the dye or carbon black mentioned above with reference toFIGS. 22, 22A. Instead, the light absorbing means is applied to theouter face of the more or less rigid container section 256'. Thelight-absorbing means can be applied as a black or dark-hued coating 268on such outer face. Alternatively, an opaque black or darkhued plasticsheet provided with a coating of pressure sensitive adhesive can besubstituted for the coating 268. The use of the dark-hued or blackcoating or sheet 268 eliminates or reduces substantially the reflectionof transmitted light back through the liquid crystal 266, after themanner of the light absorption means 16 of FIGS. 1 and 2.

1. A display device for exhibiting a varying color pattern, said devicecomprising container means having a light transmitting section, aquantity of cholesteric liquid crystalline material encapsulated withinsaid container means, said material having characteristics of selectivevisual light scattering to exhibit color patterns within a range oftemperatures at which said display device is normally utilized, and oftransmitting a substantial quantity of impinging visual light, lightabsorbing means supported by at least one of said liquid crystallinematerial and said container means for absorbing at least a substantialproportion of said transmitted light, said container means beingconfigured so as to permit substantial volumetric flow of said liquidcrystalline material within said container means, said material havingan additional characteristic of a selective light frequency scatteringwhich is variable in accordance with applied deformational stresses, thecolor patterns exhibited by said material being substantiallyinsensitive to a wide range of temperature variations, and means coupledto said container means for displacing said container means to applysaid deformational stresses to said material in a direction to inducesaid volumetric flow, said displacing means comprising a relatively thinportion of said container means adjacent said light-transmittingsection, said portion including deformable constriction and expansionareas for displacing and accommodating said flow respectively so thatpronounced color changes are effected in said material as a result ofsaid flow.
 2. The combination according to claim 1 wherein saiddisplacing means further includes an arm member engageable with anexternal surface of said container portion, means for retaining saidexternal surface and said arm member in bearing engagement, and meansfor moving said arm member across said external surface while in bearingengagement therewith.
 3. The combination according to claim 1 whereinsaid light-transmitting section is a substantially flat transparentmember of about one-eighth inch in thickness.
 4. The combinationaccording to claim 1 wherein said liquid crystalline material includesat least one of the group consisting of alkyl carbonate and alkanoiccholesteric esters of cholesterol, B-sitosterol, stigmasterol, andergosterol.
 5. The combination according to claim 4 wherein said liquidcrystalline material is a cholesteryl compound.
 6. The combinationaccording to claim 4 wherein a quantity of cholesteryl halide is admixedwith said liquid crystalline material.
 7. The combination according toclaim 6 wherein said halide is selected from the group consisting ofcholesteryl chloride, cholesteryl bromide, and cholesteryl iodide. 8.The combination according to claim 6 wherein said halide consists ofcholesteryl chloride.
 9. The combination according to claim 6 whereinsaid halide is present in the amount of about 15 to about 40 percent ofthe resulting composition.
 10. The combination according to claim 4wherein said cholesteric esters include at least one of the groupconsisting of the oleyl carbonates and the nonanoates, together with aquantity of cholesteryl halide.
 11. The combination according to claim10 wherein said oleyl carbonates include high cholesteryl oleylcarbonate and low cholesteryl oleyl carbonate.
 12. The combinationaccording to claim 11 wherein said cholesteryl halide is present in theamount of about 22 percent to about 27 percent, said high cholesteryloleyl carbonate is present in the amount of about 50 percent to about 75percent, said low cholesteryl oleyl carbonate is present in the amountof about 0 percent to about 23 percent, and said cholesteryl nonanoateis present in the amount of about 0 percent to about 15 percent.
 13. Thecombination according to claim 1 wherein said light absorbing means aresupported on said displacing means.
 14. The combination according toclaim 1 wherein said displacing means include a flexible membrane sealedto said container means so that a portion thereof can be displacedtoward said container means while another portion thereof can bedisplaced away from said container means.
 15. A display device forexhibiting a color pattern, said device comprising container meanshaving a light-transmitting section and containing a thin sandwich ofcholesteric liquid crystalline material within said container means,said material having characteristics of selective visual lightscattering to exhibit substantially temperature insensitive colorpatterns within a range of temperatures at which said display device isnormally utilized and of transmitting a substantial quantity ofimpinging visual light, light-absorbing means supported by at least oneof said liquid crystalline material and said container means forabsorbing at least a substantial proportion of said transmitted light,said container means being configured so as to permit substantialvolumetric flow of said material within said container means, saidmaterial including a quantity of cholesteryl halide and having anadditional characteristic of a selective light frequency scatteringwhich is variable in accordance with applied deformational stresses, andmeans coupled to said container means for applying said stresses. 16.The combination according to claim 15 wherein said halide is selectedfrom the group consisting of cholesteryl chloride, cholesteryl bromideand cholesteryl iodide.
 17. The combination according to claim 15wherein said halide consists of cholesteryl chloride.
 18. Thecombination according to claim 15 wherein said halide is present in theamount of about 15 percent to about 40 percent of the resultingcomposition.
 19. The combination according to claim 15 wherein saidcholesteric material includes at least one of the group consisting ofhigh and low oleyl carbonates and the nonanoates.
 20. The combinationaccording to claim 19 wherein said cholesteryl halide is present in theamount of about 22 percent to about 27 percent, high cholesteryl oleylcarbonate is present in the amount of about 50 percent to about 75percent, low cholesteryl oleyl carbonate is present in the amount of 0percent to about 23 percent, and cholesteryl nonanoate is present in theamount of 0 present to about 15 percent.